import argparse
import getpass
import os
import paramiko


def parse_encoding(data):
    try:
        enc = data.strip().decode('ascii')
    except UnicodeDecodeError:
        return

    try:
        u'unicode'.encode(enc)
    except LookupError:
        return

    return enc


def ssh_connect(hostname, **kwargs):
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy)
    ssh.connect(hostname, **kwargs)
    return ssh


def execute_command(ssh, command, **kwargs):
    _, stdout, _ = ssh.exec_command(command, **kwargs)
    return stdout.read()


def get_encoding(ssh):
    commands = [
        '$SHELL -ilc "locale charmap"',
        '$SHELL -ic "locale charmap"',
    ]

    for command in commands:
        result = execute_command(ssh, command, get_pty=True)
        # print('result:', result)
        enc = parse_encoding(result)
        if enc:
            return enc


def get_password(args):
    if args.identity:
        prompt = "{}'s passphrase: ".format(args.identity)
    else:
        prompt = "{user}@{host}:{port}'s password: ".format(
                    user=args.user, host=args.host, port=args.port
                )
    passwd = getpass.getpass(prompt).strip()
    return passwd if passwd else None


def check_identity_file(filename):
    if filename:
        if not os.path.isfile(filename):
            raise ValueError('Identity file {!r} not found'.format(filename))


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('host', type=str, help='ssh hostname')
    parser.add_argument('-u', '--user', type=str, default=os.getenv('USER'),
                        help='ssh username')
    parser.add_argument('-p', '--port', type=int, default=22,
                        help='ssh port number')
    parser.add_argument('-i', '--identity', default=None,
                        help='ssh identity file path')
    args = parser.parse_args()
    return args


def main():
    args = parse_args()
    check_identity_file(args.identity)
    pwd = get_password(args)
    ssh = ssh_connect(args.host, port=args.port, username=args.user,
                      password=pwd, key_filename=args.identity, timeout=3)
    print(get_encoding(ssh))
    ssh.close()


if __name__ == '__main__':
    main()